Our Natural Diet:
Optimal Nutrition for Health, Looks and Life
Our Natural Diet is intended to be an appealing resource that any health-interested individual will want to own. The book goes beyond the recent craze for the palaeo diet, explaining how such an approach offers only a rationale for a natural diet, but is not sufficient in itself for modern living and a world of farmed foods. Our Natural Diet offers an evidence-based approach, moving on from the wealth of background information in Human Evolution, Diet and Health, to include practical recommendations for complete health.
Our Natural Diet offers an achievable approach to complete nutrition, which in itself is the essential basis for weight-loss and good health. Supplements and many diet misconceptions are dealt with, by showing what is really beneficial and what is nothing more than simply 'popular'. Many modern diseases stem from similar dietary shortcomings, including a few unlikely culprits. The steps needed to avoid or treat these are no different to those required to help us feel better in ourselves, have more energy, achieve long-lasting weight-loss, and to be able to thrive. The information in this book can be applicable to everyone, regardless of personal dietary goals and intentions.
Our Natural Diet is absolutely not a fad diet. Everything about the book is aimed at ensuring people can follow this diet for the long-term. There is no highly restrictive or technical structure to the diet, or any complicated phases. Our Natural Diet offers long-term success and ease of adherence because it is comprised of the foods our bodies need, reducing the scope for cravings for anything else. People on this diet can help themselves to look the way they want and to feel healthy at the same time.
Excerpt: Bioaccessibility & Bioavailability
The properties of foods will differ between and within species. The age, health and diet of a food source will affect its chemical composition to some extent. As animals age their meat is likely to contain more fat, and as plant foods ripen they can increase their concentration of certain sugars and other nutrients. Processing and cooking of foods can alter the food’s nutrient content and how effectively those nutrients are absorbed across the gut into the blood. Because this varies between nutrients within the same foods, between different foods, and between cooking and processing methods, it is unrealistic to give specific details about all foods and nutrients, other than in a few key examples as we go.
In the mouth, the chewing of food helps to break it down mechanically, whilst enzymes in saliva break it down chemically. In the stomach the mechanical and chemical breakdown of food continues, as the stomach contracts and imparts compressive forces on foods to promote their digestion. The gastric fluid can disintegrate the food from the outside, and the movement of food particles against each other causes friction and shear stresses49, causing it to break up and expose a larger surface area to enzymes and stomach acid.
As foods are broken open in the stomach, the contents of cells mix with the gastric juice. This chiefly affects fats, proteins, vitamins, minerals and phytochemicals. How effectively this happens can be further affected by the total amount of food ingested, the presence of additional fluid, temperature, pH, time, viscosity and the agitation caused by stomach contractions49. In difference to the food types mentioned above, carbohydrates and their constituents are largely broken down in the mouth and gut, rather than the stomach. This is due to the enzymes in the mouth and gut being more specialised at breaking down carbohydrates than those in the stomach10.
The bioaccessibility of a substance refers to how much of it is present in the gut, and this is determined by the amount liberated from within the original foodstuff during digestion10. For example, a vitamin supplement might have a high content of vitamin E, but if the pill is not broken down during digestion, it will pass through the digestive tract with none of the vitamin E being liberated. Hence, the vitamin E content of the supplement would be high, but it would not be bioaccessible. The key to producing a good supplement or drug is to ensure the pill breaks up in the right part of the digestive tract: too early and the nutrients might be destroyed, too late and they might not be absorbed into the blood.
Bioavailability, on the other hand, refers to the amount of a nutrient that is available to the body for physiological processes or storage. So, perhaps we now have a supplement containing highly bioaccessible vitamin E, meaning that the vitamin is liberated from the pill in the right way. Because vitamin E needs to be bonded onto fat for digestion, and the pill was a solid tablet rather than an oil-filled one, the vitamin E is not absorbed into the blood unless taken with an additional source of fat. Hence, something can be highly bioaccessible but not bioavailable.
Some nutrients, such as beta-carotene in fruits and vegetables, are reduced in certain foods during cooking, but can become better absorbed as a result, whereas beta-carotene in other foods can become reduced and less absorbable due to cooking. Although this raises questions about which foods should or should not be heated to promote the bioavailability of beta-carotene, other carotenoids and many other important nutrients become more bioavailable once they are cooked. The result is that we can recommend a variety of foods, prepared in a variety of ways, with different benefits from each. Further, we ought to be sceptical about food labels listing nutritional composition, as the total amounts included will almost certainly not be what is both bioaccessible and bioavailable. This is true whether the food is a breakfast cereal with synthetic vitamins and minerals added, a supplement, or a fruit or vegetable.